1. Field of the Invention
The present invention relates to a swash plate type compressor adapted for use in an automobile refrigerating system.
2. Description of the Related Art
A swash plate type compressor has a rotatable swash plate and a plurality of pistons reciprocally moved by the swash plate. Japanese Unexamined Patent Publication (Kokai) No. 54-55809, for example, discloses a swash plate type compressor comprising a cylinder block, a rotatable swash plate and a plurality of pistons arranged in the cylinder block. The cylinder block in this Publication is formed by a front block half and a rear block half coupled together, and has at the juncture of the front and rear block halves a swash plate chamber accommodating and a suction inlet receiving a refrigerating medium from a refrigerating circuit. The swash plate chamber communicates with the suction inlet so that a lubricating oil contained in the refrigerating medium is supplied to the swash plate. The outer ends of the front and rear block halves are covered by front and rear housings, respectively, via valve plates. Each of the front and rear housing has a suction chamber and a discharge chamber formed therein, and a discharge outlet is formed in the rear housing for delivering the refrigerating medium to the refrigerating circuit. The discharge chamber of the rear housing is directly connected to the discharge outlet and the discharge chamber of the front housing is connected to the discharge outlet of the rear housing via a discharge passage.
A drive shaft extends in a central bore in the cylinder block and rotatably supported therein by radial bearings and seal elements. The swash plate is fixed to the drive shaft and accommodated in the swash plate chamber. The front and rear block halves have a plurality of pairs of front and rear working bores, each pair extending parallel to each other around the central axial bore. A plurality of double headed pistons are inserted in the respective pairs of the working bores for forming compression chambers in the working bores, respectively, and engaged with the swash plate via the shoes. Each of the valve plates has suction ports with associated valve elements for introduction of the refrigerating medium from the suction chamber of each housing to the compression chambers, and discharge ports with associated valve elements for discharge of the compressed medium from the compression chambers to the discharge chambers of the housings. Each of the front and rear block halves has a plurality of suction passages at a radially inner region of the block halves for introduction of the medium from the swash plate chamber to the suction chambers, while the discharge passage is arranged at a radially outer region of the block halves.
In this swash plate type compressor, the refrigerating medium is introduced from the refrigerating circuit into the swash plate chamber via the suction inlet, and then from the swash plate to the front and rear suction chambers. The rotation of the drive shaft is transferred to the reciprocating movement of the pistons via the swash plate. Accordingly, the refrigerating medium is sucked from each suction chamber to the compression chambers via the suction ports of the valve plates in the suction stroke of the pistons. Then the compressed refrigerating medium is discharged from the compression chambers to the discharge chambers in the front and rear housings via the discharge ports in the compression stroke. The compressed refrigerating medium in the discharge chamber in the front housing is delivered to the rear housing via the discharge passage and the compressed refrigerating medium from the front and rear discharge chambers is collected at the rear housing. The collected refrigerating medium is finally discharged from the discharge outlet to the refrigerating circuit for recirculation through the refrigerating circuit.
In the conventional swash plate type compressor, the discharge passage connecting the discharge chamber in the front housing to the rear housing must be arranged in the cylinder block in such a position that the discharge passage does not interfere with the working bores, the swash plate chamber, and the suction passages. Therefore, the discharge passage was arranged at a radially outer region of the block halves. In addition, there is a requirement to minimize the size of the compressor, and to satisfy this requirement, the discharge passage will approach the working bores, the swash plate chamber, or the suction passages. Accordingly, the refrigerating medium introduced from the refrigerating circuit in the compressor via the suction inlet and flowing through the swash plate chamber and the suction passages, is apt to be heated by the compressed and thus hot refrigerating medium flowing through the discharge passage. Then thus heated refrigerating medium is sucked in the compression chambers and compressed therein, resulting in an increase in the temperature of the compressed refrigerating medium. Therefore, the hot refrigerating medium is delivered to the refrigerating circuit at which the refrigerating medium is to be condensed, and the load of the refrigerating circuit becomes heavy and the refrigerating capacity is decreased.
The radial bearings and seal elements rotatably supporting the drive shaft are also lubricated by a mist of lubricating oil contained in the refrigerating medium flowing through the swash plate chamber the suction chamber, or the discharge chamber. However, the amount of the lubricating oil supplied to the radial bearings and seal elements is almost constant even though the revolution of the drive shaft changes, and there is a problem in that the radial bearings and seal elements may be subjected to poor lubrication when the revolution of the drive is high.